Methods of making utility knife blades

ABSTRACT

A composite utility knife blade and method of making such a blade involves butt joining a tool steel wire to a front edge of an alloy steel backing strip. The wire is electron beam welded to the backing strip to form a composite strip defining a first metal portion formed by the alloy steel backing strip, a second metal portion formed by the tool steel wire, and a weld region joining the first and second metal portions. The composite strip is then annealed, and the annealed strip is straightened to eliminate any camber therein. The annealed composite strip is then hardened such that the first metal portion defines a surface hardness within the range of approximately 38 Rc to approximately 52 Rc, and the second metal portion defines a surface hardness within the range of approximately 60 Rc to approximately 57 Rc.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is a continuation of U.S. patent applicationSer. No. 10/792,415, filed Mar. 3, 2004, entitled “Method of Making aComposite Utility Blade,” now U.S. Pat. No. 7,658,129, which is adivisional of U.S. patent application Ser. No. 09/916,018, filed Jul.26, 2001, entitled “Composite Utility Knife Blade, and Method of MakingSuch a Blade,” now U.S. Pat. No. 6,701,627, which are hereby expresslyincorporated by reference as part of the present disclosure. Thisapplication is related to U.S. patent application Ser. No. 10/202,703,filed Jul. 24, 2002, entitled “Composite Utility Knife Blade, and Methodof Making Such a Blade,” now U.S. Pat. No. 8,291,602, which is acontinuation-in-part of U.S. patent application Ser. No. 09/916,018, nowU.S. Pat. No. 6,701,627.

FIELD OF THE INVENTION

The present invention relates to utility knife blades, and moreparticularly, to composite utility knife blades wherein the outercutting edge of the blade is made of a highly wear-resistant alloy, anda backing portion of the blade is made of an alloy selected fortoughness, such as spring steel. The present invention also relates tomethods of making such composite utility knife blades.

BACKGROUND INFORMATION

Conventional utility knife blades are made of carbon steel and define aback edge, a cutting edge located on an opposite side of the bladerelative to the back edge, and two side edges located on opposite sidesof the blade relative to each other and extending between the back andcutting edges of the blade. A pair of notches are typically formed inthe back edge of the blade for engaging a locator in a blade holder.Typically, the back, cutting and side edges of the blade define anapproximately trapezoidal peripheral configuration.

Conventional utility knife blades are manufactured by providing a carbonsteel strip, running the strip through a punch press to punch thenotches at axially spaced locations on the strip, and stamping a brandname, logo or other identification thereon. Then, the strip is scored toform a plurality of axially spaced score lines, wherein each score linecorresponds to a side edge of a respective blade and defines a preferredbreaking line for later snapping the scored strip into a plurality ofblades. The punched and scored strip is then wound again into a coil,and the coil is hardened and tempered. The hardening and temperingoperations may be performed in a “pit-type” vacuum furnace wherein thecoils are repeatedly heated and cooled therein. Alternatively, thehardening and tempering operations may be performed “in-line”, whereinthe strip is unwound from the coil and successively driven through aseries of furnaces and quenching stations to harden and temper thestrip. The carbon steel strip is typically heat treated to a surfacehardness of about 58 Rockwell “c” (“Rc”), and thus defines a relativelyhard and brittle structure.

The heat treated strip is then ground, honed and stropped in aconventional manner to form the facets defining a straight cutting edgealong one side of the strip. Then, the strip is snapped at each scoreline to, in turn, break the strip along the score lines and thereby formfrom the strip a plurality of trapezoidal shaped utility knife blades.Because the entire strip is relatively hard and brittle (about 58 Rc),the strip readily breaks at each score line to thereby form clean edgesat the side of each blade.

One of the drawbacks associated with such conventional utility knifeblades is that each blade is formed of a single material, typicallycarbon steel, that is heat treated to a relatively hard and brittlestate, typically about 58 Rc. Thus, although such blades define arelatively hard, wear-resistant cutting edge, the entire blade is alsorelatively brittle, and therefore is subject to premature breaking orcracking in use. In addition, the cutting edges of such conventionalblades are frequently not as wear resistant as might otherwise bedesired. However, because the entire blade is made of the same material,any increase in hardness, and thus wear resistance of the cutting edge,would render the blade too brittle for practical use. As a result, suchconventional utility knife blades are incapable of achieving both thedesired wear resistance at the cutting edge, and overall toughness toprevent cracking or premature breakage during use. Another drawback ofsuch convention utility knife blades is that the carbon steel typicallyused to make such blades corrodes relatively easily, thus requiringpremature disposal of the blades and/or costly coatings to prevent suchpremature corrosion.

Certain prior art patents teach composite utility knife blades definingsandwiched, laminated, or coated constructions. For example, U.S. Pat.No. 4,896,424 to Walker shows a utility knife having a composite cuttingblade formed by a body section 16 made of titanium, and a cutting edgesection 18 made of high carbon stainless steel and connected to the bodysection by a dovetail joint 25.

U.S. Pat. Nos. 3,279,283, 2,093,874, 3,681,846, and 6,105,261 relategenerally to laminated knives or razor blades having cutting edgesformed by a core layer made of a high carbon steel or other relativelyhard material, and one or more outer layers made of relatively softermaterials. Similarly, U.S. Pat. Nos. 3,911,579, 5,142,785, and 5,940,975relate to knives or razor blades formed by applying a relatively hardcarbon coating (or diamond like coating (“DLC”)) to a steel substrate.In addition, U.S. Pat. Nos. 5,317,938 and 5,842,387 relate to knives orrazor blades made by etching a silicon substrate.

One of the drawbacks associated with these laminated, sandwiched and/orcoated constructions, is that they are relatively expensive tomanufacture, and therefore have not achieved widespread commercial useor acceptance in the utility knife blade field.

In stark contrast to the utility knife blade field, bi-metal band sawblades have been used in the saw industry for many years. For example,U.S. Reissue Pat. No. 26,676 shows a method of making bi-metal band sawblades wherein a steel backing strip and high speed steel wire arepre-treated by grinding and degreasing, and the wire is welded to thebacking strip by electron beam welding. Then, the composite band stockis straightened and annealed. The sides of the annealed stock are thendressed, and the band saw blade teeth are formed in the high speed steeledge of the composite stock by milling. Then, the teeth are set and theresulting saw blade is heat treated. There are numerous methods known inthe prior art for heat treating such band saw blades. For example,International Published Patent Application No. WO 98/38346 shows anapparatus and method for in-line hardening and tempering composite bandsaw blades wherein the blades are passed around rollers and drivenrepeatedly through the same tempering furnace and quenching zones. Theheat treated composite band saw blades are then cleaned and packaged.

Although such bi-metal band saw blades have achieved widespreadcommercial use and acceptance over the past 30 years in the band sawblade industry, there is not believed to be any teaching or use in theprior art to manufacture utility knife blades defining a bi-metal orother composite construction as with bi-metal band saw blades. Inaddition, there are numerous obstacles preventing the application ofsuch band saw blade technology to the manufacture of utility knifeblades. For example, as described above, conventional utility knifeblades are manufactured by forming score lines on the carbon steelstrip, and then snapping the strip along the score lines to break thestrip into the trapezoidal-shaped blades. However, the relatively tough,spring-like backing used, for example, to manufacture bi-metal band sawblades, cannot be scored and snapped. Rather, such relatively toughmaterials require different processes to form the utility knife bladesfrom a heat treated, composite strip. In addition, the heat treatingapplied to conventional utility knife blades could not be used to heattreat bi-metal or other composite utility knife blades.

Accordingly, it is an object of the present disclosure to overcome oneor more of the above-described drawbacks and disadvantages of prior artutility knife blades and methods of making such blades, and to provide abi-metal or other composite utility knife blade defining a relativelyhard, wear-resistant cutting edge, and a relatively tough, spring-likebacking, and a method of making such utility knife blades.

SUMMARY OF THE INVENTION

The present disclosure is directed to a composite utility knife bladecomprising a back edge, a cutting edge located on an opposite side ofthe blade relative to the back edge, and two side edges located onopposite sides of the blade relative to each other and extending betweenthe back and cutting edges of the blade. Preferably, the back, cuttingand side edges of the blade define an approximately trapezoidalperipheral configuration. The composite utility knife blade furtherdefines first and second metal portions, wherein the first metal portionextends between the back edge and the second metal portion, and furtherextends from approximately one side edge to the other side edge of theblade. The first metal portion is formed of an alloy steel heat treatedto a hardness within the range of approximately 38 Rc to approximately52 Rc. The second metal portion defines the cutting edge, and extendsfrom approximately one side edge to the other side edge, and is formedof a high speed or tool steel heat treated to a hardness within therange of approximately 60 Rc to approximately 75 Rc. A weld region ofthe blade joins the first and second metal portions and extends fromapproximately one side edge to the other side edge of the blade.

The present invention is also directed to a method of making compositeutility knife blades. The method comprises the steps of providing anelongated wire formed of high speed or tool steel, and an elongatedbacking strip formed of an alloy steel and defining an approximatelyplanar upper side, an approximately planar lower side, and opposing backand front edges extending between the upper and lower sides. The wire isbutt joined to the front edge of the backing strip. Then, thermal energyis applied to the interface between the wire and backing strip to weldthe wire to the backing strip and, in turn, form a composite stripdefining a first metal portion formed by the steel backing strip, asecond metal portion formed by the high speed steel wire, and a weldregion joining the first and second metal portions. The composite stripis then annealed, and the annealed strip is straightened to eliminateany camber or other undesirable curvatures in the annealed compositestrip. Then, a plurality of notches are formed, such as by punching, inaxially spaced locations relative to each other along the back edge ofthe first metal portion of the annealed composite strip. The annealedand punched composite strip is then hardened such that the first metalportion defines a surface hardness within the range of approximately 38Rc to approximately 52 Rc, and the second metal portion defines asurface hardness within the range of approximately 60 Rc toapproximately 75 Rc. The hardened strip is then subjected to at leastone, and preferably two, tempering and quenching cycles. Then, facetsare formed on the edge of the second metal portion, such as by grinding,honing and stropping, to in turn form an approximately straight, highspeed or tool steel cutting edge along the side of the composite stripopposite the back edge of the first metal portion. The composite stripis then die cut along shear lines axially spaced relative to each other.Each shear line is oriented at an acute angle relative to the back edgeof the first metal portion, and at least one notch is located betweenadjacent shear lines. The die cutting of the composite strip forms aplurality of utility knife blades, wherein each utility knife bladedefines an approximately trapezoidal peripheral configuration and atleast one notch is formed in the back edge thereof.

In accordance with an alternative embodiment of the present invention,prior to hardening, the high speed or tool steel edge of the compositestrip is cut, such as by punching, at the interface of each shear lineand the second metal portion, to thereby separate the high speed steelcutting edges of adjacent composite utility knife blades formed from thecomposite strip. Then, during the die-cutting step, only the first metalportion of the hardened composite strip is die cut along the axiallyspaced shear lines to thereby form the plurality of utility knife bladesfrom the composite strip.

One advantage of the utility knife blades and method of the presentinvention is that they provide an extremely hard, wear-resistant cuttingedge, and an extremely tough, spring-like backing, particularly incomparison to the conventional utility knife blades as described above.Thus, the utility knife blades and method of the present inventionprovide significantly improved blade life, and cutting performancethroughout the blade life, in comparison to conventional utility knifeblades. In addition, the utility knife blades, and method of making suchblades, is relatively cost effective, particularly in comparison to thecomposite utility knife blades defining sandwiched, laminated and/orcoated constructions, as also described above. As a result, the utilityknife blades and method of the present invention provide a combinationof wear resistance, toughness, cutting performance, and costeffectiveness heretofore believed to be commercially unavailable inutility knife blades.

Other objects and advantages of the present invention will becomereadily apparent in view of the following detailed description ofpreferred embodiments and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top plan view of a composite utility knife blade made inaccordance with the method of the present invention;

FIG. 2 is partial, end elevational view of the composite utility knifeblade of FIG. 1 showing the multi-faceted cutting edge of the blade.

FIGS. 3A and 3B are flow charts illustrating conceptually the proceduralsteps involved in the method of making the composite utility knifeblades in accordance with the present invention.

FIG. 4 is a somewhat schematic, perspective view of an apparatus forwelding a high speed steel wire to a spring-steel backing to formbi-metal utility knife blades in accordance with the present invention.

FIG. 5 is a somewhat schematic, perspective view of an apparatus forscoring and punching bi-metal strips in order to make bi-metal utilityknife blades in accordance with the present invention.

FIG. 6 is a somewhat schematic, perspective view of an apparatus for diecutting bi-metal strips in accordance with the present invention.

FIG. 7 is a somewhat schematic, perspective view of an apparatus forpunching notches in the high-speed steel edges of the bi-metal stripsprior to hardening the strips in accordance with the present invention,and the resulting notched strip.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In FIG. 1, a composite utility knife blade made in accordance with themethod of the present invention is indicated generally by the referencenumeral 10. The utility knife blade 10 defines a back edge 12, a cuttingedge 14 located on an opposite side of the blade relative to the backedge, and two side edges 16, 18 located on opposite sides of the bladerelative to each other and extending between the back and cutting edgesof the blade. As shown typically in FIG. 1, the back, cutting and sideedges of the blade preferably define an approximately trapezoidalperipheral configuration.

The blade 10 further defines a first metal portion 20 and a second metalportion 22. As shown typically in FIG. 1, the first metal portion 20extends between the back edge 12 and the first metal portion 22, andfurther extends from approximately one side edge 16 to the other sideedge 18. In accordance with the present invention, the first metalportion 20 is formed of a steel, typically referred to as an “alloy”steel, that is heat treated to a surface hardness within the range ofapproximately 38 Rockwell “c” (referred to herein as “Rc”) toapproximately 52 Rc. The second metal portion 22 defines the cuttingedge 14 and extends from approximately one side edge 16 to the otherside edge 18. In accordance with the present invention, the second metalportion 22 is formed of a steel, typically referred to as a “high speed”or “tool” steel, that is heat treated to a surface hardness within therange of approximately 60 Rc to approximately 75 Rc.

The first metal portion 20 defines a spring-like backing that isrelatively pliable, tough, and thus highly resistant to fatigue andcracking. The second metal portion 22, on the other hand, is relativelyhard and highly wear resistant, and thus defines an ideal, long-lastingcutting blade. As a result, the composite utility knife blades made inaccordance with the method of the present invention define highlywear-resistant, long-lasting cutting edges, combined with virtuallyunbreakable or shatter-proof backings. Thus, in stark contrast to thetypical utility knife blades of the prior art, the composite utilityknife blades made in accordance with the method of the present inventionprovide a cost-effective blade exhibiting both improved wear resistanceand toughness heretofore commercially unavailable in such blades.

The first metal portion 20 of blade 10 is preferably made of any ofnumerous different grades of steel capable of being heat treated to asurface hardness within the preferred range of approximately 38 Rc toapproximately 52 Rc, such as any of numerous different standard AISIgrades, including 6135, 6150 and D6A. The second metal portion 22, onthe other hand, is preferably made of any of numerous different types ofwear-resistant steel capable of being heat treated to a surface hardnesswithin the preferred range of approximately 60 Rc to approximately 75Rc, such as any of numerous different standard AISI grades, including,without limitation, M Series grades, such as M1, M2, M3, M42, etc., ASeries grades, such as A2, A6, A7 A9, etc., H Series grades, such asH10, H11, H12, H13, etc., and T Series grades, such as T1, T4, T8, etc.

As may be recognized by those skilled in the pertinent art based on theteachings herein, the currently preferred materials used to constructthe first and second metal portions 20 and 22 and disclosed herein areonly exemplary, and numerous other types of metals that are currently orlater become known for performing the functions of the first and/orsecond metal portions may be equally employed to form the compositeutility knife blades in accordance with the present invention.

As further shown in FIG. 1, each composite utility knife blade 10defines a pair of cut outs or notches 24 formed in the back edge 12 andlaterally spaced relative to each other. As shown typically in FIG. 1,each notch 24 defines a concave, approximately semi-circular profile,and is provided to engage a corresponding locator mounted within a bladeholder (not shown) in order to retain the blade in the blade holder. Asmay be recognized by those skilled in the pertinent art based on theteachings herein, the notches 24 may take any of numerous differentshapes and/or configurations, and the blade may include any number ofsuch notches or other recesses that are currently or later become knownto those skilled in the pertinent art for performing the function ofengaging a blade holder, or the blade actuating mechanism or locator ofsuch a holder.

As also shown in FIG. 1, the blade 10 further defines a registrationaperture 26 extending through the first metal portion in anapproximately central portion of the blade. As described further below,the registration aperture 26 is provided to receive a blade positioningdevice to position the blade in a die cutter during the process ofmaking the blades in accordance with the present invention. As may berecognized by those skilled in the pertinent art based on the teachingsherein, the aperture 26 may take any of numerous different shapes orconfigurations, and the blade may include any number of such aperturesor other structural features for performing the function of properlypositioning the blade in a die cutting or other manufacturing apparatus.In addition, the registration aperture(s) 26 may be located in any ofnumerous different locations on the utility knife blade, or may belocated within the scrap material adjacent the blade and within thebi-metal strip from which the blade is formed.

As further shown in FIG. 1, the blade 10 defines a weld region 28 formedbetween the first and second metal portions 20 and 22, respectively, anddefining an approximate line of joinder extending from one side edge 16to the other side edge 18. As described in further detail below, thesecond metal portion is joined to the first metal portion 20 by applyingthermal energy to the interface, such as by electron beam welding, tothereby weld the first metal portion to the second metal portion andform a resulting weld region defining a line of joinder between the twodifferent metal portions.

As also shown in FIG. 1, the cutting edge 14 defines an approximatelystraight cutting edge extending from one side edge 16 to the other sideedge 18. As shown in FIG. 2, the cutting edge 14 preferably definesfirst facets 30 located on opposite sides of the blade relative to eachother, and second facets 32 spaced laterally inwardly and contiguous tothe respective first facets 30. As shown typically in FIG. 2, the firstfacets 30 define a first included angle “A”, and the second facets 32define a second included angle “B”. Preferably, the second includedangle B is less than the first included angle A. In the currentlypreferred embodiment of the present invention, the first included angleA is approximately 26° and the second included angle B is approximately18°. However, as may be recognized by those skilled in the pertinent artbased on the teachings herein, these included angles are only exemplaryand may be set as desired depending upon the physical properties and/orproposed applications of the blade. As may be further recognized bythose skilled in the pertinent art, the utility knife blades made inaccordance with the method of the present invention may include anynumber of facets.

Turning to FIGS. 3A and 3B, the method of making the composite utilityknife blades in accordance with the present invention is hereinafterdescribed in further detail. As shown at steps 100 and 102, the backingsteel forming the first metal portion 20 and the high speed or toolsteel wire forming the second metal portion 22 are cleaned and otherwiseprepared for welding in a manner known to those of ordinary skill in thepertinent art. As shown in FIG. 4, the backing steel is preferablyprovided in the form of one or more continuous elongated strips 34 woundinto one or more coils. Each backing strip 34 defines an approximatelyplanar upper side 36, an approximately planar lower side 38, andopposing back and front edges 40 and 42, respectively. Similarly, thehigh speed or tool steel wire is preferably provided in the form of oneor more continuous lengths of wire 44 wound into one or more coils.

At step 104 of FIG. 3A, the high speed or tool steel wire 44 is buttjoined to the front edge 42 of the backing strip 34, and thermal energyis applied to the interface between the wire and the backing strip to,in turn, weld the wire to the backing strip and form a bi-metal orcomposite strip 46 defining the first metal portion 20 formed by thesteel backing strip 34, the second metal portion 22 formed by the highspeed steel wire 44, and the weld region 28 joining the first and secondmetal portions. As shown in FIG. 4, a typical welding apparatus 48includes opposing rollers 50 laterally spaced relative to each other forbutt joining the high speed steel wire 44 to the front edge 42 of thebacking strip 34, and rotatably driving the composite or bi-metal strip46 through the welding apparatus. A thermal energy source 52 is mountedwithin the welding apparatus 48 and applies thermal energy to theinterface of the high speed steel wire 44 and front edge 42 of thebacking strip to weld the wire to the backing strip. In the currentlypreferred embodiment of the present invention, the thermal energy source52 transmits an electron beam 54 onto the interface of the high speedsteel wire and backing strip to electron beam weld the wire to thebacking strip. However, as may be recognized by those skilled in thepertinent art based on the teachings herein, any of numerous otherenergy sources and/or joining methods that are currently or later becomeknown for performing the functions of the electron beam weldingapparatus may be equally employed in the method of the presentdisclosure. For example, the energy source for welding the high speedsteel wire to the backing strip may take the form of a laser or otherenergy source, and welding processes other than electron beam weldingmay be equally used.

As shown at step 106 of FIG. 3A, after welding the wire to the backingstrip, the bi-metal strip 46 may then be coiled for annealing and/or fortransporting the strip to an annealing station. As shown at step 108,the bi-metal strip 46 is annealed in a manner known to those of ordinaryskill in the pertinent art. Typically, the bi-metal strips 46 areannealed in a vacuum furnace of a type known to those of ordinary skillin the pertinent art wherein a plurality of coils are vertically mountedrelative to each other on a thermally conductive rack, and the rack ismounted in an evacuated furnace to soak the coils at a predeterminedannealing temperature for a predetermined period of time. In thecurrently preferred embodiment of the present invention, the bi-metalstrips 46 are annealed at a temperature within the range ofapproximately 1400° F. to approximately 1600° F. for up to approximately5 hours. Then, the heated coils are allowed to cool at a predeterminedrate in order to obtain the desired physical properties. For example,the coils may be cooled within the evacuated furnace initially at therate of about 50° F. per hour until the coils reach approximately 1000°F., and then the coils may be allowed to cool at a more rapid rate. Asmay be recognized by those skilled in the pertinent art based on theteachings herein, these temperatures and times are only exemplary,however, and may be changed as desired depending upon any of numerousdifferent factors, such as the particular materials, constructionsand/or dimensions of the bi-metal strip 46, the type of welding processused to weld the wire to the backing, and/or the desired physicalproperties of the resulting blades.

After annealing, the bi-metal strip 46 is then uncoiled, if necessary,as shown at step 110, and the strip is straightened, as shown at step112. After welding and annealing, the bi-metal strip 46 may develop asignificant camber or other undesirable curvatures, and therefore suchcurvatures must be removed prior to further processing. In the currentlypreferred embodiment of the present invention, the bi-metal strip 46 ismechanically straightened by passing the strip through a series ofpressurized rolls in a straightening apparatus of a type known to thoseof ordinary skill in the pertinent art, such as the Bruderer™ brandapparatus. However, as may be recognized by those skilled in thepertinent art based on the teachings herein, any of numerousstraightening apparatus that are currently or later become known forperforming the function of straightening metal articles like thebi-metal strip 46 may be equally employed. For example, as analternative to the mechanical straightening apparatus, the bi-metalstrip 46 may be straightened by applying heat and tension thereto in amanner known to those of ordinary skill in the pertinent art.

As shown at step 114, the straightened bi-metal strip 46 may be coiledagain, if necessary, for transportation and further processing. As shownat step 116 of FIG. 3B, the annealed and straightened bi-metal strip 46is then uncoiled, if necessary. At step 118, the bi-metal strip ispunched to form a plurality of notches or other cut outs 24 axiallyspaced relative to each other along the back edge 40 of the annealedbi-metal strip, and is scored to form a plurality of shear linesdefining the side edges 16 and 18 of each blade. As shown in FIG. 5, atypical apparatus for performing the punching and scoring operations onthe bi-metal strip 46 is indicated generally the reference numeral 56.The apparatus 56 includes a scoring instrument 58 mounted on a support60 above a work support surface 62 supporting the bi-metal strip 46thereon. As indicated by the arrows in FIG. 5, the scoring instrument ismovable vertically into and out of engagement with the bi-metal strip,and is movable laterally relative to the strip. Thus, as shown typicallyin FIG. 5, the scoring tool 58 is controlled to engage the upper surface36 of the bi-metal strip and move laterally across the strip to, inturn, score the upper surface of the strip and thereby form a pluralityof score lines 64 axially spaced relative to each other on the strip andeach defining a side edge 16 or 18 of a respective utility knife blade10 (FIG. 1). The apparatus 56 further includes a punch 66 defining aplurality of cutting surfaces 68, each corresponding in shape andposition to a respective notch 24 and aperture 26. As shown in FIG. 5,the punch 56 is drivingly connected to drive source 70, such as ahydraulic cylinder, and is movable into and out of engagement with thebi-metal strip seated on the work support surface 62 for cutting thenotches 24 and aperture 26 in the bi-metal strip. As will be recognizedby those of ordinary skill in the pertinent art based on the teachingsherein, the scoring tool 58 and punch 66 may be computer-controlled toautomatically drive the scoring tool and punch into and out ofengagement with the bi-metal strip, and a driving mechanism (not shown)may be employed to automatically index the bi-metal strip relative tothe scoring tool and punch. Similarly, the scoring tool and punch may bemounted in different apparatus or work stations than each other, and/ormay each take the form of any of numerous other tools that are currentlyor later become known for either applying the score lines to thebi-metal strip, or cutting the notches and/or apertures in the bi-metalstrip.

As shown at step 120 of FIG. 3B, the punched and scored bi-metal strip46 may be coiled again, if necessary, for either temporary storage ortransportation to the hardening and tempering stations. At step 122, thebi-metal strip is then uncoiled, if necessary, and at step 124, theuncoiled strip is hardened and tempered. As may be recognized by thoseof ordinary skill in the pertinent art based on the teachings herein,the hardening and tempering operations may be performed in accordancewith any of numerous different hardening and tempering processes andapparatus that are currently known, or later become known for hardeningand tempering articles like the bi-metal strip 46. In the currentlypreferred embodiment of the present invention, the bi-metal strip 46 ishardened at a temperature within the range of approximately 2000° F. toapproximately 2200° F. for a hardening time period within the range ofabout 3 to about 5 minutes. Then, after hardening, the bi-metal strip istempered within a first tempering cycle at a temperature within therange of approximately 1000° F. to approximately 1200° F. for atempering time within the range of about 3 to about 5 minutes. After thefirst tempering cycle, the bi-metal strip is quenched by air cooling toroom temperature. In the currently preferred embodiment of the presentinvention, the hardening and tempering cycles are performed “in-line”such that the bi-metal strip is continuously driven first through anelongated hardening furnace, then through a first elongated temperingfurnace, then through a quenching station, and then through at least onemore tempering furnace and quenching station. However, as may berecognized by those of ordinary skill in the pertinent art based on theteachings herein, the bi-metal strip may be repeatedly passed throughthe same tempering furnace and quenching station(s), and/or may be woundinto coils and hardened, tempered and quenched in a “pit-type” or otherfurnace. In addition, the quenching may be an air quench as describedherein, or may be an oil quench or other type of quench that iscurrently, or later becomes known for quenching tempered articles of thetype disclosed herein. Similarly, the composite strip may be subjectedto any number of tempering and quenching cycles as may be required inorder to obtain the desired physical characteristics of the resultingblades.

At step 126, the tempered and quenched bi-metal strip 46 is coiledagain, if necessary, for transportation to the next tempering station,and at step 128, the bi-metal strip is uncoiled for the second temperingcycle. As discussed above, these and other coiling and uncoiling stepscan be eliminated by providing one or more in-line stations forprocessing the bi-metal strip. At step 130, the bi-metal strip istempered again within a second tempering cycle at a temperature withinthe range of approximately 1000° F. to approximately 1200° F. for atempering time within the range of about 3 to about 5 minutes. After thesecond tempering cycle, the bi-metal strip is quenched to roomtemperature. In the currently preferred embodiment, the quench is an airquench; however, as discussed above, this quench may take the form anyof numerous other types of quenching processes that are currently orlater become known for articles of the type disclosed herein. Then, atstep 132 the tempered and quenched bi-metal strip is coiled again eitherfor temporary storage and/or transportation to the grinding and punchingstations.

At step 134, the annealed, hardened and tempered bi-metal strip 46 isuncoiled again, if necessary, and at 136, the bi-metal strip issubjected to grinding, honing, stropping, and die-cutting or bend andsnap steps. More specifically, the bi-metal strip 46 is ground, honedand stropped in a manner known to those of ordinary skill in thepertinent art to form the facets 30 and 32 of FIG. 2, and thereby definea straight, high-speed or toolsteel cutting edge along the side of thecomposite strip opposite the back edge of the first metal portion. Then,the ground, honed and stropped bi-metal strip 46 is die cut or bent andsnapped along the score or shear lines 64 of FIG. 5 to thereby form aplurality of utility knife blades from the composite strip, wherein eachutility knife blade defines an approximately trapezoidal peripheralconfiguration with the notches 24 and central aperture 26 formedtherein, as shown typically in FIG. 1.

As shown in FIG. 6, a typical apparatus for die cutting the bi-metalstrip is indicated generally by the reference numeral 72. The apparatus72 comprises male and female dies 74 and 76, respectively, wherein thefemale die 76 is connected to a shaft 78 and the shaft is, in turn,drivingly connected to a hydraulic cylinder or like drive source 80 formoving the female die 78 into and out of engagement with the bi-metalstrip 46 overlying the male die 74. The male die 74 includes a locatorpin 82 projecting upwardly therefrom and received within the apertures26 of the bi-metal strip to thereby properly locate the bi-metal stripbetween the male and female dies. As shown in phantom in FIG. 6, thefemale die 76 includes blade-like edges 84, and the male die 74 includesopposing blade-like edges 86 overlying and underlying respectively theshear lines 64 of the portion of the bi-metal strip 46 received betweenthe dies. Then, in order to die cut the strip, the drive source 80 isactuated to drive the female die 76 downwardly and into engagement withthe bi-metal strip such that the female and male blade-like edges 84 and86, respectively, cooperate to shear the bi-metal strip along the shearlines and thereby form a respective utility knife blade, as showntypically in FIG. 1. During this die-cutting operation, because of therelative hardness of the first and second metal portions 20 and 22,respectively, of the bi-metal strip, the strip is sheared by theblade-like edges along the score lines 64 within the first metal portion20, and is snapped by the blade-like edges along the portions of thescore lines within the relatively hard and brittle second portion 22.Thus, the score lines provide desired break lines (or a desired “crackpath”) within the relatively hard and brittle second metal portion, andtherefore are important to providing clean and sharp edges in theseregions of the blades.

In accordance with an alternative embodiment of the present invention,and as shown typically in FIG. 7, the bi-metal strip 46 may be punchedprior to hardening at step 124 in order to avoid the need to later cutthe relatively hard and brittle high speed steel edge at step 136, andthereby prevent any possible damage to the cutting edge 14 and facets 30and 32 formed thereon that might otherwise occur during die-cutting. Asshown typically in FIG. 7, an apparatus for punching the high-speedsteel edge in accordance with the present invention is indicatedgenerally by the reference numeral 88. The apparatus 88 includes a punchor like tool 90 mounted on a tool support 92 over a work support surface94 for supporting the bi-metal strip 46 thereon. The tool support 92 isdrivingly connected to a hydraulic cylinder or like drive source 96 fordriving the punch 90 into and out of engagement with the high speedsteel edge 14 of the bi-metal strip 46. As shown typically in FIG. 7,the punch 90 is shaped and configured to form a notch 98 at theinterface of each score line 64 and the high speed steel edge or secondmetal portion 22. Thus, as shown typically in FIG. 7, each notch 98extends along the respective score line at least throughout the secondmetal portion 22 of the score line to thereby separate the high speedsteel portion of the respective blade from the remainder of the bi-metalstrip at the score lines. Then, when the bi-metal strip 46 is die cut asshown in FIG. 6, the dies need only cut the first metal portion 20 ofthe strip along the score lines and need not die cut the high speedsteel edge portions. As described above, the first metal portion 20 isrelatively pliable and significantly less hard than the second metalportion 22, and therefore the first metal portion 20 may be easily andcleanly die cut along the score lines 64. After hardening, the secondmetal portion 22 may be relatively difficult to die cut because of therelative hardness and brittleness of this portion. However, prior tohardening, the high speed steel edge exhibits a surface hardness withinthe range of about 25 Rc, and therefore may be relatively easily andcleanly punched at this stage of the process. Accordingly, thealternative process and construction of FIG. 7 may facilitate theability to avoid any damage to the hardened, high speed steel edge, thatmight otherwise occur when die cutting such edge.

The notches 98 of FIG. 7 are shown as v-shaped notches. However, as maybe recognized by those of ordinary skill in the pertinent art, thesenotches or cut outs may take any of numerous different shapes that maybe required to separate the high speed steel edge portions of each bladefrom the remainder of the composite strip at the score or shear lines.As may be further recognized by those skilled in the pertinent art basedon the teachings herein, it may be possible in the alternativeembodiment of the present invention to eliminate the score lines becausethe score lines may be unnecessary in certain circumstances for purposesof die cutting the first metal portion 20 of the bi-metal strip.

Turning against to FIG. 3B, at step 138 the blades are stacked, and atstep 140, the stacked blades are packaged in a manner known to those ofordinary skill in the pertinent art.

As may be recognized by those skilled in the pertinent art based on theteachings herein, numerous changes and modifications may be made to theabove-described and other embodiments of the composite utility knifeblades and the methods of making such blades of the present inventionwithout departing from the scope of the invention as defined in theappended claims. For example, although the composite utility knifeblades 10 illustrated herein define a bi-metal construction, the bladesmade in accordance with the present invention may equally define atri-metal or other composite construction. For example, the utilityknife blades made in accordance with the present invention may equallydefine high speed or tool steel cutting edges formed on opposite sidesof the blade relative to each other, with a relatively tough,spring-like portion formed between the outer high speed or tool steeledges. Similarly, a tri-metal strip may be cut down the middle, orotherwise cut along an axially-extending line to form two bi-metalstrips which each may, in turn, be cut to form the blades in accordancewith the present invention. In addition, many, if not all, of thecoiling and uncoiling steps shown in FIGS. 3A and 3B may be eliminatedby employing in-line processing apparatus. Moreover, the blades need notnecessarily define a trapezoidal peripheral configuration, but rathermay define a rectangular or other peripheral configuration as desired orotherwise required by a particular tool or application. Accordingly,this detailed description of preferred embodiments is to be taken in anillustrative, as opposed to a limiting sense.

What is claimed is:
 1. A method of making a utility knife blade, comprising: providing a utility knife blade body having first and second portions formed of different alloys and an approximately trapezoidal shape defined by a first edge, a second edge, a third edge located on an opposite side of the utility knife blade relative to the second edge, and a fourth edge located on an opposite side of the utility knife blade relative to the first edge; providing the first edge with at least one notch therein; and providing the fourth edge with at least one cutting edge having at least two facets located on opposite sides of the utility knife blade relative to each other; wherein the method further comprises heat treating the second portion to a hardness within the range of approximately 60 Rc to approximately 75 Rc and the first portion to a hardness that is less than the second portion, the first portion extending between the first edge and the second portion and between the second edge and the third edge, the second portion defining the cutting edge and extending between the second edge and the third edge on an opposite side of the first portion relative to the first edge, and an interface between the first and second portions extending from approximately the second edge to approximately the third edge of the utility knife blade, wherein the step of heat treating occurs after the step of providing the utility knife blade body.
 2. A method as defined in claim 1, further comprising providing the second portion adjoining the first portion.
 3. A method as defined in claim 1, further comprising providing the interface to extend continuously from the second edge to the third edge of the utility knife blade.
 4. A method as defined in claim 1, further comprising providing the utility knife blade body to define a line of joinder between the first and second portions.
 5. A method as defined in claim 1, further comprising providing the at least one cutting edge to define an approximately straight edge.
 6. A method as defined in claim 5, further comprising providing the at least one cutting edge to extend from approximately the second edge to approximately the third edge of the utility knife blade.
 7. A method as defined in claim 1, further comprising providing a corner at each end of the cutting edge, wherein each corner is formed by a surface that is one of (i) rounded, (ii) oriented approximately perpendicular to the cutting edge, and (iii) oriented at an oblique angle to the cutting edge.
 8. A method as defined in claim 1, wherein the step of providing a utility knife blade body comprises providing a shatter-proof utility knife blade.
 9. A method as defined in claim 1, further comprising providing a plurality of said utility knife blades integral with each other in a strip, the first edge of each of said plurality defined by a first edge of the strip, the cutting edge of each of said plurality defined by a second edge of the strip, and providing score lines axially spaced relative to each other on the strip and extending between the first and second edges of the strip to form side edges of each of said plurality.
 10. A method as defined in claim 9, further comprising providing a plurality of notches axially spaced relative to each other along the second edge of the strip, providing each of said plurality of notches at the interface of one of the score lines and the second portion.
 11. A method as defined in claim 10, wherein the step of providing the plurality of notches further comprises providing each notch extending along its respective score line at least throughout the second portion.
 12. A method as defined in claim 1, further comprising providing a plurality of said utility knife blade integral with each other in a strip, the first edge of each of said plurality defined by a first edge of the strip, the cutting edge of each of said plurality defined by a second edge of the strip, and providing a plurality of indentations axially spaced relative to each other along the second edge, providing each of the plurality of indentations extending through the second portion.
 13. A method as defined in claim 12, wherein the step of providing each of the plurality of indentations comprises providing said indentations in the form of an approximately v-shaped notch.
 14. A method of making a utility knife blade, comprising: providing first and second means for defining an approximately trapezoidal shape defined by a first edge, a second edge, a third edge located on an opposite side of the utility knife blade relative to the second edge, and a fourth edge located on an opposite side of the utility knife blade relative to the first edge wherein the first and second means are formed of different alloys; providing the first edge with at least one notch therein; providing the fourth edge with at least one cutting edge having at least two facets located on opposite sides of the utility knife blade relative to each other; wherein the step of providing the fourth edge with the at least one cutting edge comprises providing the first means with a wear-resistant metal cutting edge defining a hardness within the range of approximately 60 Rc to approximately 75 Rc and extending from approximately the second edge to approximately the third edge; providing the second means with a hardness that is less than the first means and extending between the first edge and the first means and from approximately the second edge to approximately the third edge; and providing an interface between the first and second means extending from approximately the second edge to approximately the third edge of the utility knife blade, wherein the step of providing the first means with a wear-resistant metal cutting edge defining a hardness within the range of approximately 60 Rc to approximately 75 Rc occurs after the step of providing the first and second means.
 15. A method as defined in claim 14, further comprising providing the first means adjoining the second means.
 16. A method as defined in claim 14, further comprising providing the interface to extend continuously from the second edge to the third edge of the utility knife blade.
 17. A method as defined in claim 14, further comprising providing a line of joinder between the first and second means.
 18. A method as defined in claim 14, further comprising providing the first means to define an approximately straight cutting edge extending from approximately the second edge to approximately the third edge of the utility knife blade.
 19. A method as defined in claim 14, wherein the step of providing the second means comprises providing a steel strip and the step of providing the second means with a hardness that is less than the first means comprises heat treating the second means to a hardness that is less than the first means.
 20. A method as defined in claim 14, wherein the step of providing the first and second means comprising providing shatter-proof first and second means.
 21. A method of making a utility knife blade, comprising: providing a utility knife blade body having first and second portions formed of different alloys and an approximately trapezoidal shape defined by a first edge, a second edge, a third edge located on an opposite side of the utility knife blade relative to the second edge, and a fourth edge located on an opposite side of the utility knife blade relative to the first edge; providing the first edge with at least one notch therein; and providing the fourth edge with at least one cutting edge having at least two facets located on opposite sides of the utility knife blade relative to each other; wherein the method further comprises heat treating the first portion to a first hardness and the second portion to a second hardness greater than the first hardness, the first portion extending between the first edge and the second portion and between the second edge and the third edge, the second portion defining the cutting edge and extending between the second edge and the third edge on an opposite side of the first portion relative to the first edge, and an interface between the first and second portions extending from approximately the second edge to approximately the third edge of the utility knife blade, wherein the step of heat treating occurs after the step of providing the utility knife blade body.
 22. A method as defined in claim 21, further comprising providing the second portion adjoining the first portion.
 23. A method as defined in claim 21, further comprising providing the interface to extend continuously from the second edge to the third edge of the utility knife blade.
 24. A method as defined in claim 21, further comprising providing the utility knife blade body to define a line of joinder between the first and second portions.
 25. A method as defined in claim 21, further comprising providing the at least one cutting edge to define an approximately straight edge extending from approximately the second edge to approximately the third edge of the utility knife blade.
 26. A method as defined in claim 21, wherein the step of heat treating the second portion comprises heat treating the second portion to a second hardness within the range of approximately 60 Rc to approximately 75 Rc.
 27. A method as defined in claim 21, wherein the step of providing a utility knife blade body comprises providing a shatter-proof utility knife blade.
 28. A method of making a utility knife blade, comprising: providing a first means for defining a wear-resistant metal cutting edge defining a first end, a second end, at least two facets located on opposite sides of the utility knife blade relative to each other, and a first hardness; providing a pliable second means for defining a second hardness that is less than the first hardness extending from approximately the first end to approximately the second end of the metal cutting edge, on an opposite side of the first means relative to the metal cutting edge, and on an opposite side, relative to the first means, of an interface between the first and second means that extends from approximately the first end to approximately the second end of the metal cutting edge, wherein the first means and the pliable second means are formed of different alloys; providing at least one notch in the second means; and providing the first means and the second means so as to define an approximately trapezoidal shape.
 29. A method as defined in claim 28, further comprising providing the second means adjoining the first means.
 30. A method as defined in claim 28 further comprising providing the interface extending continuously from the first end to the second end.
 31. A method as defined in claim 28, further comprising providing a line of joinder between the first and second means.
 32. A method as defined in claim 28, further comprising providing the first means to define an approximately straight cutting edge.
 33. A method as defined in claim 28, further comprising providing the first means to extend from approximately one side edge to approximately another side edge of the utility knife blade.
 34. A method as defined in claim 28, further comprising providing the second means to extend between a back edge and the first means, and to extend from approximately one side edge to approximately another side edge of the utility knife blade.
 35. A method as defined in claim 28, wherein the step of providing the first means comprises heat treating steel to the first hardness within the range of approximately 60 Rc to approximately 75 Rc.
 36. A method as defined in claim 28, wherein the step of providing the second means comprises heat treating steel to the second hardness.
 37. A method of making a utility knife blade, comprising: providing a utility knife blade body having first and second portions formed of different alloys and an approximately trapezoidal shape defined by a first edge, a second edge, a third edge located on an opposite side of the utility knife blade relative to the second edge, and a fourth edge located on an opposite side of the utility knife blade relative to the first edge; providing the first edge with at least one notch therein; and providing the fourth edge with at least one cutting edge having at least two facets located on opposite sides of the utility knife blade relative to each other; wherein the method further comprises providing the first portion with a first hardness and heat treating the second portion to a second hardness greater than the first hardness, the first portion extending between the first edge and the second portion and between the second edge and the third edge, the second portion defining the cutting edge and extending between the second edge and the third edge on an opposite side of the first portion relative to the first edge and an interface between the first and second portions extending from approximately the second edge to approximately the third edge of the utility knife blade, wherein the step of providing the first portion with a first hardness and heat treating the second portion occurs after the step of providing the utility knife blade body.
 38. A method as defined in claim 37, further comprising providing the second portion adjoining the first portion.
 39. A method as defined in claim 37, further comprising providing the interface extending continuously from the second edge to the third edge of the utility knife blade.
 40. A method as defined in claim 37, further comprising providing the utility knife blade body to define a line of joinder between the first and second portions.
 41. A method as defined in claim 37, further comprising providing the at least one cutting edge to define an approximately straight edge extending from approximately the second edge to approximately the third edge of the utility knife blade.
 42. A method as defined in claim 37, wherein the step of heat treating the second portion comprises heat treating the second portion to the second hardness within the range of approximately 60 Rc to approximately 75 Rc.
 43. A method as defined in claim 37, wherein the step of providing a utility knife blade body comprises providing a shatter-proof utility knife blade.
 44. A method of making a utility knife blade, comprising: providing a utility knife blade body having a pliable first portion formed of steel, a second portion formed of steel, and an approximately trapezoidal shape defined by a first edge, a second edge, a third edge located on an opposite side of the utility knife blade relative to the second edge, and a fourth edge located on an opposite side of the utility knife blade relative to the first edge, wherein the pliable first portion and the second portion are formed of different alloys; providing the first edge with at least one notch therein; and providing the fourth edge with at least one cutting edge having at least two facets located on opposite sides of the utility knife blade relative to each other; wherein the method further comprises providing the first portion with a first hardness and heat treating the second portion to a second hardness greater than the first hardness, the first portion extending between the first edge and the second portion and between the second edge and the third edge, the second portion defining the cutting edge and extending between the second edge and the third edge on an opposite side of the first portion relative to the first edge and an interface between the first portion and the second portion extending from approximately the second edge to approximately the third edge of the utility knife blade.
 45. A method as defined in claim 44, wherein the step of heat treating the second portion comprises heat treating the second portion to a hardness within a range of approximately 60 Rc to approximately 75 Rc. 